-- Sale of Last Non-Core Business Completes Company's Strategic

Refocusing on Its Satellite Systems and Launch Vehicle Businesses --

DULLES, Va.April 17, 2008--Orbital Sciences Corporation (NYSE:ORB) announced today that it has reached a definitive agreement with Affiliated Computer Services, Inc. (ACS) (NYSE:ACS) for the sale of its non-core Transportation Management Systems (TMS) unit. ACS has agreed to pay $42.5 million for the TMS business, subject to customary closing conditions, in an all-cash transaction expected to close this summer.

"The sale of the TMS unit is the final step in Orbital's strategic refocusing on its core business of designing, manufacturing and operating satellites and rocket systems," said Mr. David W. Thompson, Orbital's Chairman and Chief Executive Officer. "The TMS business has experienced robust growth, solid profit margin expansion and improved cash flow over the past several years, enabling us to realize an appropriate value for the business. At the same time, ACS is well positioned to expand upon TMS' success, thereby benefiting the employees who will be transitioning to ACS with the close of the transaction, as well as existing and prospective customers."

TMS is a leading integrator of software-based systems that combine satellite navigation and wireless communications to enable municipal transit and other fleet operators to better manage and dispatch public transit and highway service vehicles and commuter light rail systems. TMS offers its products and services to the global Intelligent Transportation Systems market, including its state-of-the-art Computer Aided Dispatch and Automatic Vehicle Location solutions. TMS currently serves approximately 60 state, regional and local transit agency customers in the US and abroad and has units installed or scheduled to be installed on nearly 30,000 vehicles in those markets.

About Orbital

Orbital develops and manufactures small rockets and space systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low Earth-orbit, geosynchronous Earth-orbit and planetary spacecraft for communications, remote sensing, scientific and defense missions; human-rated space systems for Earth-orbit, lunar and other missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense systems that are used as interceptor and target vehicles. Orbital also offers space-related technical services to government agencies and develops and builds software-based transportation management systems for public transit agencies and private vehicle fleet operators.

More information about Orbital can be found at http://www.orbital.com

    CONTACT: Orbital Sciences Corporation
             Barron Beneski, 703-406-5528
             Public and Investor Relations

    SOURCE: Orbital Sciences Corporation